When constructing a multi-story building, the framing system is generally the load bearing structure that supports the building. Commercial framing, for example, typically consists of vertical steel beams with horizontal beams spanning between them. The floor of each story is typically a concrete slab that rests upon the horizontal beams of the framing structure. This floor slab can be steel reinforced concrete and can be attached to, or poured around, the framing beams. The framing system is designed to carry all of the anticipated floor and roof loads as well as provide stabilization against horizontal forces due to, for example, wind and seismic loads. The floor slab in particular is generally required to transmit such forces to building lateral systems, such as moment frames, braced frames, and shear walls, provided throughout the framing system in order to satisfy the minimum design requirement per building code.
In recent years, revisions to the national and international building code standards have increased lateral load requirements for seismic design criteria, especially the requirements for multi-story building construction. As a result, the framing systems of most prospective multi-story building structures will be required to resist lateral loads greater than those able to be accommodated by existing structural framework. Because of the increased seismic design criteria and the continuing pressure of minimizing construction costs, among other things, new design alternatives for structural framing systems have been developed to meet all current loading requirements imposed upon modern multi-story buildings in an economical and cost-effective manner. One of the recent developments in the field of building construction is to use prefabricated building components, such as precast concrete slab and wall panels, steel structures and other elements that can be manufactured in controlled environment. These precast concrete components are widely used in modern building construction. These prefabricated components can be easily erected and assembled in construction sites to greatly reduce the cost, fieldwork, and construction duration. U.S. Pat. No. 4,505,087, entitled “Method of construction of concrete decks with haunched supporting beams,” discusses a method of construction of concrete decks utilizing precast members over which concrete is poured to form a monolithic structure. One problem associated with structures built from the precast concrete components is the overall integrity. U.S. Pat. No. 4,081,935 A, entitled “Building structure utilizing precast concrete elements,” discusses a construction method for improving the structural integrity of such structures by applying cast concrete over the precast concrete slab panels and beams. However, there are other integrity problems left unanswered. For example, in some situations, structural steel and precast concrete members are desired to be used together in constructing a building. Currently, technologies for integrating these two types of materials are underdeveloped, which, as a result, inevitably hinders constructions based on these types of materials.
Another recent design alternative for a structural framing system is described in U.S. Pat. No. 6,442,908 wherein a dissymmetric steel beam having a narrowed, thickened top flange, a widened bottom flange, and a web having trapezoidal openings extending therebetween is adapted to be horizontally disposed between adjacent vertical steel columns that are erected upon conventional foundations. Standard hollow core sections of precast concrete plank are assembled together perpendicularly to the open web dissymmetric beam. The planks are supported by the bottom flange on either side, such that the open web of the beam is centrally disposed between end surfaces of the plank sections in substantially the same horizontal plane. A high-strength grout mixture applied to the assembled beam and plank sections is made to flow completely through the web openings in a circulatory manner thereby creating a substantially monolithic concrete encasement around the dissymmetric beam. This improves the resulting composite action and mechanical interlock between the steel beam and concrete plank and reduces loss of strength due to separation of the grout from either side of the beam.
While initial testing indicates that the framing system of the aforementioned patent has increased load bearing, testing has also indicated a need to enhance the composite action. In response, embodiments of the present technology relate to an open-web shear connector composite beam system, which combines some of the benefits of the conventional open-web castellated beam system and composite construction. In this configuration, the precast beams can act with steel beams, and can greatly increase the bending strength of the beams. The open web composite shear connectors can also act compositely with the base beam to further increase the bending strength of the system. Precast concrete planks and/or panels can be easily set on the steel beams with no interference from beam flanges during erection. The open-web of the composite shear connectors can enable the precast concrete deck to be integrated with the steel beam to provide required composite action. Reinforcement can be added and can provide, for example, additional shear strength, ductility, and toughness. Improved and increased ductility can greatly improve the seismic resistant characteristics of a structure. This improvement may be further enhanced if precast concrete filigree panels are utilized.
The system can be utilized for building within a wide range of span lengths. The system also provides a wide range of load capacities, which can enable the system to meet the demands of, for example and not limitation, residential, industrial, and commercial applications. The use of precast concrete panels can also reduce construction duration significantly. Precast panels can also minimize weather delays, since conditions such as humidity, precipitation, and temperature no longer affect the ability to pour and properly set concrete (i.e., the panels can be precast and cured in controlled conditions and then transported to the job site).